I was wondering why people are frightened of the idea of Zombies and where the crossover was between puppets and animatronics, critically the part that breeches a human being's comfort zone, dipping into fear and deep distrust. The condition is called Uncanny Valley and is caused by a figure breaks through the wall of emulating human behaviour to the point that it almost convinces, but not quite. It is why The Polar Express (2004) was seen as 'eerie' rather than 'heartwarming' (though actually, I really like the film). I think that it is the eyes that are the give away. Robot engineers have not got the eyes right, yet they are close. They have pretty much nailed the body language aspect - but!!! There are flickers of human expression that are so quick that neither CGI nor animatronic experts have been able to emulate it. The actions are also completely random, so unless they configured an algorythm that itself was random, the overall effect would still look contrived.